INTERSTITIAL LASER THERMOTHERAPY OF ADENOCARCINOMA TRANSPLANTED INTO RAT-LIVER

Objective: To examine the effect of different temperatures and exposur e times in interstitial laser thermotherapy. Design: Controlled labora tory study. Setting: University hospital, Sweden. Material: 48 male Wi star FU rats with dimethylhydrazine-induced adenocarcinoma transplante d into the liver. Intervention: Treatment was given with an Nd:YAG las er and a feedback system for temperature regulation. Light was deliver ed into the centre of the tumour and the feedback thermistor probe was placed 3 mm from the tumour margin. Rats were treated at steady-state temperatures at the feedback thermistor of 43, 46, or 50 degrees C fo r 30 minutes, and at a steady-state temperature of 46 degrees C at the feedback thermistor also for 10 and 20 minutes. Main outcome measurem ent: Tumour control as assessed 6 days after treatment using light mic roscopical examination including immunohistochemical determination of bromodeoxyuridine (BrdU) incorporation into DNA as a measure of cell v iability. Results: Complete tumour necrosis was achieved in all rats t reated for 30 minutes, in 6/8 rats treated for 10 minutes and in 6/8 r ats treated for 20 minutes at 46 degrees C. During steady-state thermo therapy, temperatures at the tumour margin were about 11 degrees highe r than at the feedback thermistor (range 54-61 degrees C). The surroun ding liver tissue also became necrotic so that the total necrosis volu me exceeded the pretreatment tumour volume. Conclusion: Interstitial l aser thermotherapy at temperatures ranging from 54-61 degrees C at the tumour margin ensures total necrosis of a transplanted rat liver carc inoma provided that treatment is given for 30 minutes.